SANAA, Yemen -- Five people, including four South Korean tourists, were killed by an explosion in the Yemeni province of Hadramout, the government said Monday.

The Yemeni Interior Ministry said in a news release that the explosion, whose fifth victim was a Yemeni guide, occurred in a mountainous Hadramont area, the official Yemeni government news agency, Saba, said.

"The explosion occurred about 2:45 GMT (6:45 P.M. in Sanaa) while a number of South Korean tourists were paying a visit to a mountainous area in the historical city of Shibam, Hadramout," the ministry said.

"Five other South Koreans, two men and three women, suffered light injuries due to the incident."

Another Yemeni national was hurt in the explosion, unidentified security sources added.

The cause of the blast has yet to be determined but the sources told Saba the incident is under investigation by security services.